#include<bits/stdc++.h>
using namespace std;
string a, b;
vector<int> A, B;

bool grteq(vector<int>&A, vector<int>&B) {
    if(A.size()!=B.size()) return A.size()>B.size();
    else {
        for(int i=A.size()-1; i>=0; --i) {
            if(A[i]!=B[i]) return A[i]>B[i];
        }
    }
    return true;
}
int main() {
    cin>>a>>b;
    for(int i=a.size()-1; i>=0; i--) A.push_back(a[i]-'0');
    for(int i=b.size()-1; i>=0; i--) B.push_back(b[i]-'0');
    if(not grteq(A, B)) {
        swap(A, B);
        cout<<'-';
    }
    vector<int> C;
    int t = 0;
    for(int i=0; i<A.size(); ++i) {
        t = A[i] - t;
        if(i<B.size()) t -= B[i];
        C.push_back((t+10)%10);
        if(t<0) t = 1;
        else t = 0;
    }
    while(C.size()>1 && C.back()==0) C.pop_back();
    for(int i=C.size()-1; i>=0; --i) cout<<C[i];
    cout<<endl;
}